I found a piece of pipe in the scrap metal pile at work yesterday. A galvanized 4"x12" nipple in the middle, with a coupler on one side and a solid brass 4" camlock plug on the other. It's just waiting to be built into a hybrid, HGDT says that with a 20X mix (probably not safe, I haven't calculated burst pressures yet), and 4 lb 4" projectile, I would get 73000 Ft/lbs.But the matching aluminum camlock socket would set me back about $50, brass or SS about $150, and the bushings to go down to 1/2" so I can connect it to a pump and propane would be another $50-100, not to mention the barrel...needless to say that without a job I am strapped for cash and I can build many more smaller launchers with that money, and a giant hybrid probably shouldn't be my second cannon.

Also, we have a LOT of metal electrical conduit at work that I can use. Mostly 1" and 1-1/2", but I found a few pieces of 3/4", 1-1/4" and 3". Do these have any use in spudding? Most are unthreaded for use with compression fittings, but a few 1-1/4" conduits have threads on them. Other than the issue with the seam, can these be used as barrels? What about on a hybrid? How high of a mix could I take them too? Found a couple couplers too, I could do a 60' barrel if I had a big enough chamber and enough space.